[avalanche] Fix the getavaaddr functional test

Summary:
The interval test is not testing what it expects because it checks for receipt of address twice, but:

• the reception list is not cleared in between
• there should be no addr message because there is no new addr to send
• the getavaaddr message might even not be processed (yet) when the test assumes it is

This diff fixes these issues and check no extra message is sent.

Test Plan:

./test/functional/test_runner.py abc_p2p_getavaaddr

Reviewers: #bitcoin_abc, PiRK

Reviewed By: #bitcoin_abc, PiRK

Differential Revision: https://reviews.bitcoinabc.org/D17076